All seven games of Huskies football? And the 16 home games of of Huskies basketball?
The Mariners and Sounders (who average 33,000 fans) play in the summer.

What makes it so hard in Seattle when the exact same thing occurs in Minnesota, Boston, Denver, Detroit, Chicago, New York, Washington, and Philadelphia?

They said for years that Washington DC was a Redskins only town and nobody would support anything else. Well, MLB brought the Nats in and they draw. The Caps you can't get a ticket for (I know, I tried). Perpetually sold out. The Caps get significant media coverage in the DC metro area. Pretty much every game is on TV and radio, the newspapers devote good chunks of their sports sections to the team. People actually TALK about the Caps. If anything it's the NBA Wizards that get the snickers and eyerolls.